Sheldon Silver arrives at court for his sentencing in New York on May 3, 2016.

Photographer: Gregg Vigliotti/The New York Times

Good government groups and other critics of state lawmakers reacted with outrage Thursday to the federal appeals court decision that reversed former Assembly Speaker Sheldon Silver's 2015 corruption conviction.

"Sheldon Silver is absolutely guilty of corrupting his office and violating the public trust for 19 million New Yorkers," said Susan Lerner, executive director of Common Cause New York.

The Lawsuit Reform Alliance of New York, based in Albany, said the decision opens the door to more corruption and a "government for sale" attitude at the state Capitol.

"If using public money to buy lucrative clients isn't corrupt, I don't know what is," said Tom Stebbins, executive director of the alliance.

The reversal of Silver's conviction for soliciting payments to his New York City law firm in return for providing millions of dollars in state money to a cancer research institution in the city is the second time in less than a decade that a high-profile corruption conviction of an Albany politician has been reversed after a U.S. Supreme Court decision. In each case, the reversal was based on the trial judge having given erroneous instructions to the jury, based on U.S. Supreme Court rulings not yet in effect.

In 2012, the conviction — three years earlier — of former Senate majority leader Joe Bruno of Rensselaer County was overturned after the U.S. Supreme Court narrowed the definition of what qualifies as corruption under the federal "honest services" law. Bruno was tried a second time in 2014 and was acquitted.

The most recent Supreme Court decision — one cited by the appeals court in reversing Silver's conviction — found that former Virginia Gov. Bob McDonnell and his wife had not committed a crime, even though they accepted vacations, loans and valuable gifts from a businessman and the governor promoted the man's company's diet supplement product.

Lerner said the appeals court misinterpreted the law, and the facts underlying Silver's conviction are not in question.

"Overturning Mr. Silver's conviction based on the judge's instructions to the jury, which occurred before the McDonnell ruling, does not redefine the facts in evidence," she said. "The U.S. Attorney's Office under Preet Bharara's leadership won its case, and we have every expectation that the people can win again on retrial."

The U.S. Attorney's Office for the Southern District of New York said it plans to retry Silver.

Bharara — who was fired in April by President Donald J. Trump — wrote in a Twitter post:

The evidence was strong. The Supreme Court changed the law. I expect Sheldon Silver to be retried and re-convicted.

A professor at Albany Law School who has followed New York state corruption cases closely said the Second Circuit got it right, given the revised standard set by the Supreme Court.

"I wasn't very surprised," professor Vincent Bonventre said. "The prosecution certainly proved he engaged in conduct that seemed unethical, but it in fact (was) completely ethical under the law."

Silver was accused of receiving $4 million for referring a client — one who subsequently received state research funding — to his law firm. The move may look improper, Bonventre said, but it may not be.

"There is absolutely nothing unethical under the rules of the legal profession with an attorney being compensated for a referral to a law firm, whether that attorney does any other work or not," he said.

He said nobody who has followed the Supreme Court's reviews of the "honest services" law — which states it is a federal crime for an official to deprive the public of his or her "honest services" — should have been surprised by the McDonnell ruling, or Thursday's.

The problem with Silver's conviction, he said, is that the judge's instructions didn't require the jury to find a specific corrupt act.

"In order to be guilty of violating the honest services law, the politician must have engaged in a very official act or a very formal act that was analogous to a vote or to a specific determination," Bonventre said. "The United States Supreme Court said politicians wielding influence on behalf of constituents is not unlawful, and it would probably be unconstitutional for a law to be written prohibiting that."

In any retrial, the prosecution would have to meet the higher standard set in the McDonnell case.

Silver was convicted Nov. 30, 2015, of honest services fraud, extortion and money laundering in one of the most prominent corruption trials in New York City in decades.

Silver was sentenced to 12 years in prison by the judge, but he was allowed to remain free pending his appeal. He automatically lost his Assembly seat upon conviction.

The cost of Silver's prosecution hasn't been disclosed. If his acquittal were to stand, he could ask the state for reimbursement of his defense costs, as Bruno did. Bruno was reimbursed $1.8 million and gave most of it to the state Senate Republican Campaign Committee and Tech Valley High School.